Method and apparatus for continuous grease manufacture



J. H. GREENE ETAL Original Filed Dec.

Oct. 28, 1969 METHOD AND APPARATUS FOR CONTINUOUS GREASE MANUFACTUREUnited States Patent US. Cl. 252-39 20 Claims ABSTRACT OF THE DISCLOSUREContinuous process and apparatus for the preparation of soap thickenedgrease compositions including the steps of saponification anddehydration, wherein a saponifiable material and a metal base arecontinuously intro duced at an elevated temperature into asaponification zone maintained at superatmospheric pressure andsaponified under turbulent conditions characterized by a Reynolds numberof at least 4000, the saponified product is blended with lubricating oilto provide a grease mixture containing at least oil, the grease isdehydrated at an elevated temperature and subatmospheric pressure, andany additional oil required is added thereto to form a grease of thedesired grade.

This invention relates to an improved method and apparatus for themanufacture of soap thickened greases. More particularly, it relates toan improved method and apparatus for carrying out the preparation ofsoap thickened greases in a continuous operation including a continuoussaponification step.

Continuous processes of various types which have been proposedheretofore for the manufacture of lubricating greases have not beenemployed successfully in actual grease plant operations, althoughsemicontinuous processes, employing preformed soaps, have been employedfairly successfully in the manufacture of certain greases. The failureof the prior art to provide a successful wholly continuous grease makingprocess is due primarily to the criticality of the process conditionsduring the steps of the process wherein the soap fibers are principallyformed, and the difficulty in carrying out these steps rapidly in acontinuous process so as to obtain both an economically feasiblethroughput rate and satisfactory yields and product quality. Inaddition, the apparatus designed for carrying out the continuousprocesses of the prior art are generally lacking in flexibility, and aretherefore not capable of producing greases of ditferent types requiringvery different process conditions. Equipment of the type required for acontinuous grease making operation which can be employed only in theproduction of a grease of one particular type is ordinarily noteconomically justified in grease plant operations. For these reasons,continuous grease making processes are not employed commercially inspite of the very considerable inherent advantages of continuous overbatch operations generally.

The present invention provides a convenient and flexible method andapparatus for the manufacture of lubricating greases in a continuousoperation under conditions which are readily controllable so as toproduce optimum yields and product quality. As a particularlyadvantageous embodiment, it provides a small, compact and inexpensiveapparatus capable of producing soap thickened greases of variousdifferent types of superior quality in high yields and with extremelyhigh throughput rates, resulting in a production capacity equivalent tothat of a large scale commercial grease kettle or other conven-3,475,335 Patented Oct. 28, 1969 ICC tional grease making equipment. Anapparatus of this type which has been operated very successfully in themanufacture of various greases occupies a floor space of only 8 x 11feet x 8 feet in height, and has a throughput rate up to about 2,000pounds per hour. This capacity is substantially equivalent to that of alarge grease kettle, requiring a two-story building for housing, takinginto consideration the filling and waiting times required in theoperation of the latter. Such an apparatus can be economicallyconstructed and operated at locations where grease is required in largequantities, or it can be truckmounted for transportation between suchlocations, thus obviating expensive packaging or bulk shipments, whichrequire specially equipped tankcars.

The grease making process of this invention comprises saponification,dehydration and soap conditioning steps carried out in a continuousmanner with recycling of the grease mixture through a shear valve duringthe soap conditioning step. In the preferred embodiments of theinvention, the saponification step is carried out in such a manner thata high degree of turbulence is maintained in the saponification mixtureduring the reaction. The process also preferably comprises a cooling andfinishing step, which may be carried out by the addition of lubricatingoil at a lower temperature than the grease mixture or by passing thegrease mixture through a cooler. Very advantageously, it may be carriedout by a combination of these two methods, and with shearing of thegrease mixture within a suitable temperature range either during orafter the cooling.

The apparatus which the invention provides for carrying out this greasemaking process comprises a single zone for the dehydration and soapconditioning steps, provided with a recycle line containing a shearvalve for recycling the grease mixture from the bottom to the top of thezone with shearing of the recycle stream, and adapted to be operated ata substantially lower pressure than the saponification zone. Thesaponification zone is preferably a flow type reactor, very suitablycomprising a section of pipe having an inside diameter of about 0.5-1.25inches, and preferably provided with a recycle system for recycling thesaponification mixture through the reactor at a sufficient rate tomaintain turbulent flow. The apparatus preferably comprises a finishingsection also, with provisions for cooling the grease mixture either bythe addition of cold lubricating oil or by passing it through a heatexchanger. An apparatus representing a particularly preferred embodimentof the invention comprises a finishing section wherein the greasemixture may be recycled through a shearing means, such as a shear valve,either during or after this cooling.

In carrying out the process under the preferred conditions, thesaponification zone is maintained at an elevated temperature andpressure at least sufficient to maintain the water present in thesaponification mixture in the liquid phase, and the dehydration zone isoperated at an elevated temperature below the melting point of the soapand under a substantially lower pressure than the saponification zone,so that the major portion of the water is flashed off when the greasemixture enters the dehydration zone. Any remaining water is removedduring recycling of the grease mixture through the shear valve, which ineffect subjects the grease mixture to a continuous flashing operation bypressure release of the re cycle stream through the valve. The recyclingis preferably carried out at a rapid rate, such that the grease mixtureis subjected to multiple passes through the shear valve operated with atleast a substantial pressure drop during the residence time of thegrease mixture within the zone. Cooling of the grease mixture ispreferably carried out with the addition of lubricating oil at asubstantially lower temperature than the grease mixture, and veryadvantageously in some cases with recycling of the grease mixturethrough a cooler. The process is also carried out very advantageously insome cases with recycling of the grease mixture through a shearing meansduring or after the cooling at a temperature within a range which willvary somewhat with the different greases, depending chiefly upon thecharacter of the soap thickener.

Greases of excellent quality are obtained in the above manner in goodyields and in greatly reduced manufacturing times as compared with theprior art processes, due in a large measure to the effect upon the soapfiber development of the recycle shearing during the dehydration andsoap conditioning steps, and also to the combined effect of thisshearing with the effect of carrying out the saponification underturbulent conditions, which provides a grease mixture wherein the soapmolecules or micelles are present in a highly dispersed state.

The invention will be better understood from the following descriptionin conjunction with the accompanying drawing, which is a schematicdiagram of an apparatus representing a preferred embodiment of theinvention.

Referring to the drawing, 1 is a tubular reactor in the form of a coil,situated inside chamber 2 and connected with lines 6 and 7. Chamber 2 issealed by flange 3 and provided with inlet line 4 and outlet line 5 forsteam or other heating fluid. Vessel 15 contains saponifiable material,or a mixture of saponifiable material and lubricating oil, which ismaintained at a temperature above the melting point of the saponifiablematerial by heating means 16. Ordinarily, vessel 15 will contain amixture of saponifiable material and lubricating oil comprising at leastpercent by weight of the mixture. It is generally preferred to employ amixture comprising about 20 to 60 percent by weight of saponifiablematerial, although lower amounts down to about 5 percent by weight andalso higher amounts up to 100 percent by weight of saponifiable materialmay be employed in some cases. Vessel 20 contains a water solution oroil slurry of metal base.

In carrying out the grease making process, the saponifiable materialpasses at a controlled rate through line 17 containing valve 18 and pump19 into line 24, while a solution or slurry of metal base passes fromtank 20 at a controlled rate through line 21 containing valve 22 andpump 23 into line 24. From line 24 the mixture of saponifiable materialand metal base passes through line 25 into line 7 at the intake of pump10, and from pump 10 it passes through line 6 into zone 1. When thesaponification is carried out employing a slurry of the metal base inoil, it is generally desirable to introduce a small amount of water orsteam into the reaction zone in order to promote the reaction. Thereaction mixture in reaction zone 1 is maintained under superatmosphericpressure at least sufficient to maintain the water present or producedin the reaction in the liquid phase, and at an elevated temperaturesuflicient to obtain a rapid reaction between the metal base and thesaponifiable material. Suitable reaction conditions include broadlypressures in the range from about 10 to about 300 pounds per square inchgauge and temperatures from about 180 F. up to above the melting pointof the soap formed in the reaction. The preferred conditions includepressures in the range from about 50 pounds per square inch to about 200pounds per square inch and temperatures in the range from about 200 F.to about 350 F.

The reactant stream is passed through reaction zone 1 at a velocitywhich is preferably suflicient to maintain turbulent flow within thezone. With special advantage, the reactant stream may be passed throughthe reaction zone at a velocity resulting in highly turbulent flow,preferably at a velocity resulting in a Reynolds number in the rangefrom about 4,000 to about 100,000. Flow rates required to obtain thedesired degree of turbulence are generally within the range from about0.6 to about 12.0 cubic feet per minute per square inch of reactor crosssection. In the process comprising the preferred embodiment of thisinvention, the saponification mixture is recycled continuously throughreactor 1 by way of lines 6 and 7 and pump 10, as a means of obtaining asufliciently high rate of flow of the reactant stream through thesaponification zone. In this manner, a high rate of flow throughreaction zone 1 is maintained which is not dependent upon the feed rate,and turbulent flow through the reaction zone can therefore be maintainedeven with a saponification mixture requiring a relatively long residencetime for substantially complete reaction or where an input rate belowthat required for turbulent flow is required by other conditions of theprocess. The recycle rate employed is ordinarily in the ratio from about1021 to about :1 with the rate of throughput, although somewhat lower orhigher recycling ratio may be employed in some cases, such as recycleratio as low as about 1:1 and as high as about 200: 1.

Saponification products obtained under the above conditions areespecially suitable for use in the subsequent grease making steps of ourprocess because of the readiness with which they accept additionallubricating oil and the shorter soap conditioning periods which theyrequire as compared with grease mixtures obtained under othersaponification conditions. The different physical conditions of theseproducts are shown by the fact that they form grease-like productsimmediately upon cooling when the saponification mixture containslubricating oil, differently from saponification products obtained underdifferent conditions including such products obtained in reactors whereturbulence is maintained by other means. This different result ispresumably due to the severe shearing to which the reaction mixture issubjected when it is passed through a relatively small diameter tubeunder turbulent flow conditions.

A product stream from reaction zone 1 passes to dehydration zone 30 byway of line 7 and line 26 containing valve 27. Dehydration zone 30 is anupright zone of relatively large diameter as compared with zone 1,sealed by flange 31 and provided with line 32 which is connected to apressure regulator means (not shown). It may be jacketed or otherwiseprovided with indirect heating or cooling means. The grease mixture inzone 30 is maintained at an elevated temperature above about 225 F. andordinarily at least about 250 F., but below the melting point of thesoap present in the grease mixture, and at a pressure substantiallylower than that in reaction zone 1, very suitably under a partial vacuumof from about 5 to about 25 inches of mercury. In the prepara tion oflithium 12-hydroxystearate thickened greases, the grease mixture in zone30 is preferably maintained at a temperature in the range from about 350F. to about 375 F.

During its residence in zone 30, the grease mixture is recycledcontinuously through line 33, containing pump 34 and valves 35 and 37.Valve 37 is a shear valve, suitably a gate valve, set in a partiallyclosed position so as to give a pressure drop of about 10-200 pounds persquare inch, and preferably about 25-125 pounds per square inch acrossthe valve. The recycling is preferably carried out at a rapid rate, suchthat the volume of recycled grease mixture is equal to the total averagevolume of grease mixture within zone 30 (1 batch turnover) Within oneminute, and suflicient to provide at least about 5 batch turnovers, andmost advantageously at least 10 batch turnovers, during the averageresidence time of the grease mixture within the zone. The greaseresidence time in zone 30 may be only sufficient to obtain substantiallycomplete dehydration of the grease mixture, the soap conditioning stepin this case taking place simultaneously with the final dehydrationstages. It is ordinarily prolonged somewhat so as to provide anadditional soap conditioning period, preferably for at least about 5minutes, particularly when the dehydration is accomplished substantiallyentirely in the initial flashing operation. In carrying out the processunder the preferred conditions, the residence time of the grease mixturein zone 30 may be from a few minutes up to about 1 hour, dependingchiefly upon the character of the soap in the grease mixture, and to aless extent upon other factors such as temperature, soap concentrationof the grease mixture and character of the lubricating oil. In thepreparation of lithium and calcium hydroxy fatty acid soap thickenedgreases, a suitable residence time of the grease mixture in zone 30 willusually be from about 5 to about 20 minutes, although somewhat shorteror longer periods may be employed in some cases.

Additional lubricating oil from tank 40 may be added to the greasemixture at various steps in the process in order to obtain the desiredsoap concentration or to as sist in heating or cooling the greasemixture. This additional oil may pass into the grease mixture in line 26by Way of line 41, containing valve 42, line 43 containing pump 44 andvalve 45, and line 49 containing valve 50. Additional lubricating oil isadded very advantageously in this manner so as to provide at least aboutpercent of lubricating oil in the grease mixture in line 26 when thesaponification is carried out with no lubrieating oil or only a smallamount of lubricating oil present in the saponification mixture. Suchoil addition may also be employed as a means of heating the greasemixture in order to increase the water removal when the grease mixtureis flashed into zone 30. The oil added for this purpose is preheated bypassing through heater 46 by way of line 43a, containing valve 45a.

Additionally or alternatively, lubricating oil from tank 40 may passinto the saponification mixture in zone 1 by passing from line 43through line 47 containing valve 48 and into line 25. Oil added in thismanner is employed either in addition to or in place of lubricating oilemployed in admixture with the saponifiable material in tank 15. It ispreferably preheated in heater 46, very suitably to a temperature inabout the range 150- 350 F.

Additionally or alternatively to the lubricating oil addition in theabove manner, lubricating oil may be added from tank 40 to the greasemixture during the soap conditioning step. The oil added at this stageof the process may pass into the grease mixture in zone 30 through line51 containing valve 52. With special advantage in some cases, it maypass through line 53 containing valve 54, into the recycle stream ofgrease mixture in line 33 as the means of aiding in the recycling when aheavy grease mixture is being circulated, and also as a means ofincreasing the rate of dehydration by increasing the temperature of therecycle stream in some cases. Additional oil is added in the abovemanner as required to provide a grease mixture in zone 30 containing atleast about 25 percent by weight of lubricating oil, and preferably atleast about 40 percent by weight of lubricating oil.

In addition to the function of the lubricating oil addition to thegrease mixture in zone 30 as a means of obtaining the desired soapconcentration, the oil addition may be employed as a means of eitherheating or cooling the grease mixture to a temperature within thedesired soap conditioning temperature range. When the saponification iscarried out at a temperature above the melting point of the soap, theoil added to the grease mixture in zone 30 by way of lines 51 or 53 ispreferably at a lower temperature than the grease mixture leaving thesaponification zone. When the saponification is carried out at atemperature below the desired temperature range for the soapconditioning treatment, the lubricating oil added as described above ispreferably preheated. The temperature of the lubricating oil and theamount added may be adjusted so as to give the desired soapconcentration in the grease mixture in zone 30 and also to provide atemperature within the desired soap conditioning temperature range.

Indirect heating or cooling of the grease mixture in zone 30 may beemployed either in addition or alternatively to the heating or coolingobtained by oil addition as described above. The indirect heating orcooling may be obtained very conveniently by employing a jacketed vesselfor zone 30 and passing a heat exchange fluid through the vessel jacket.Very advantageously in some cases, the indirect heating or cooling isapplied to the recycle stream of grease mixture in line 33 by passingthe grease mixture through heat exchanger 36 by Way of line 33a,containing valve 35a. It is, for example, particularly advantageous insome cases to cool the recycle stream in this manner in order to obtainan increased effect by the shearing, due to the more viscous greasemixture obtained by the coolmg.

A stream of substantially dehydrated grease mixture is continuouslywithdrawn from the recycle stream in line 33 by way of line 75containing pump 76. Additional lubricating oil may be added to thegrease mixture in line 75 from tank 60 by way of line 61 containingvalve 62 and line 66 containing pump 67 and valve 68. It is ordinarilypreferable to add this oil at a temperature substantially lower thanthat of the grease mixture, very suitably in some cases at ambienttemperature. However, in many cases it is advantageous to preheat theoil by passing it through heat exchanger 70 by way of line 6612,containing valve 68a, particularly where a high rate of oil addition isemployed or where it is desirable to employ a slower cooling rate.Alternatively or additionally, oil may be introduced into line 75 fromtank 40 by way of line 41, line 64, containing valve 65, and line 66.Tank 60 is generally employed in conjunction with tank 40 in the processonly when two different lubricating oils are employed in the grease.

The additional oil added to the grease mixture in line 75 may amount toas much as about 90 percent by weight of the total oil in the finishedgrease. It is ordinarily preferable to carry out the grease preparationwith about 20- percent by weight of the total oil contained in thegrease added in this manner at a temperature at least about 100 F. belowthe temperature of the grease mixture in line 75.

From line 75 the grease mixture passes into line 79, containing pump 80and valves 81 and 83. Valve 81 is a shear valve, such as a gate valve,which may be operated with a substantial pressure drop. Where it isdesirable to obtain additional cooling, the grease mixture may passthrough cooler 85, by way of line 79a, containing valve 83a. Recyclingof the grease mixture through line 79 by way of line 89 may be employedin order to obtain multiple passes through shearing valve 81 and cooler85. From line 79 a stream of the grease mixture is taken off throughline 87, containing valve 88. Additional lubricating oil at the same ora lower temperature may be added to this stream of grease mixture by wayof line 71, containing valve 72, either alternatively or in addition tothe lubricating oil added through line 66 as described above. Whenadditional oil is added in this manner it becomes mixed with the greasemixture as the combined steam passes through valve 88, which is operatedas a shear valve. The stream of grease mixture containing oil added inthis manner may pass through additional shearing means if desired.

Any additives employed in the grease are preferably introduced into thegrease mixture during the cooling, ordinarily where the grease mixtureis below about 250 F. As shown in the diagram, the additives may beadded from tank 90 by way of line 91 containing valve 92 and pump 93into the grease mixture in line 75 after the addition of lubricating oilfrom line 66. When the grease mixture at this point is not at a suitablylow temperature, the additives may be added at some later point in thecooling and finishing section In the manufacture of cup greases, thewater of stabilization is also added during the finishing when thegrease mixture is at a temperature below 210 F.

It is ordinarily advantageous to recycle the grease mixture throughshear valve 81 operated with a pressure drop in about the range 20-200pounds per square inch gauge, employing a recycle ratio from about 1:1to about 100:1 and preferably from about 5:1 to about 50:1. Shearing inthis manner is preferably carried out upon the grease mixture at atemperature below about 300 F., and most advantageously in most cases ata temperature within the range from about 250 F. to about 150 F.

The metal base employed in the saponification may be a hydroxide orother suitable basic reacting compound of any of the metals ordinarilyemployed as the metal component of the soap in the preparation oflubricating greases, such as sodium, lithium, potassium, calcium,barium, magnesium, zinc, cobalt, manganese aluminum, lead, etc., as wellas mixtures of two or more metals. It is preferably a metal oxide,hydroxide or carbonate. The greases which are most advantageouslyprepared by the method of this invention are those wherein the soapthickener is an alkali metal or alkaline earth metal soap, or a mixtureof two or more soaps of these classes.

Suitable saponifiable materials for use in these grease preparationscomprise higher fatty acids containing from about 12 to 32 carbon atomsper molecule and hydroxy substituted higher fatty acids, theirglycerides and other esters and mixtures thereof. The invention alsocontemplates grease preparations carried out in the manner describedabove wherein such higher fatty acid materials are employed inconjunction with lower fatty acid materials, such as fatty acidscontaining from one to about 6 carbon atoms per molecule, theirglycerides and other esters, Such lower fatty acid materials may beemployed in amounts giving a mol ratio of lower fatty acid to higherfatty acid from below 1:1 up to about 20:1, respectively. Also,intermediate fatty acid materials may be employed in conjunction withthe higher fatty acid materials in varying amounts, ordinarily inamounts giving a mo1 ratio with the higher fatty acid material belowabout 1:1, respectively.

The oleaginous liquids employed in these greases may be any suitableoils having lubricating characteristics, including the conventionalmineral lubricating oils, synthetic oils obtained by various refiningprocesses such as cracking and polymerization and other syntheticoleaginous compounds such as high molecular weight ethers and esters.The dicarboxylic acid esters, such as di-Z-ethylhexyl sebacate,di(secondary amyl)sebacate, di-Z-ethylhexyl azelate, diisooctyl adipate,etc., comprise a particularly suitable class of synthetic oils and maybe employed either as the sole oleaginous component of the grease or incombination with other synthetic oils or mineral oils. Suitable mineraloils for use in these greases are those having viseosities in the rangefrom about 100 to about 8000 seconds Saybolt Universal at 100 R, whichmay be blends of low and high viscosity oils. They may be eithernaphthenic or paraffinic in type, or blends of two or more oils of thesedifferent types.

In the production of greases from synthetic oils which are hydrolyzedunder the saponification conditions, the saponification is preferablycarried out in the absence of any lubricating oil or of a minor amountof a lubricating oil which is substantially inert under thesaponification conditions such as a mineral oil and the synthetic oiladded at later stages of the grease making process as describedhereinabove.

The following examples are illustrative of lubricating greasepreparations carried out in accordance with this invention.

EXAMPLE I A lithium l2-hydroxystearate thickened grease was prepared bythe method of this invention as described below.

The apparatus employed in the preparation comprised a coil reactor, adehydrator and a cooler, with auxiliary equipment for circulating thegrease mixture through each of these zones as shown in the figure, aswell as for introducing reactants and additional lubricating oil, movingthe grease mixture between the zones and withdrawing a product stream.The reactor consisted of a 21-foot section of inch Schedule 40 blackiron pipe (0.824 inch inside diameter) formed into a coil having a 4inch inside diameter and mounted in a 3 foot section of 12 inch pipeserving as a steam chamber. The recycle line on the reaction zonecomprised 9 feet of inch pipe containing a recycle pump, which was aViking Rotary heavy duty pump having a capacity of 18 gallons per minuteat 1200 revolutions per minute. The capacity of the reactor and recycleline including the pump was 0.12 cubic foot. The dehydrator comprised a3 foot section of 10 inch Schedule 40 black iron pipe with a blindflange and a bell cap on the ends and electrically heated by a wrappingof resistance wire on the outside. The recycle line on the dehydratorconsisted of a 5 foot section of 0.824 inch inside diameter pipecontaining a recycle pump of the same type as that employed in therecycle line on the reactor and a Fulflo valve. The dehydrator wasconnected at the top by a 2.067 inch inside diameter pipe to a vacuumjet with a condenser. The reactor and dehydrator were connected by a0.824 inch inside diameter pipe containing Fulflo valve. The cooler wasa watercooled Graham Helifiow shell and tube type exchanger, throughwhich the grease mixture was circulated at 18 gallons per minute,resulting in turbulent flow.

The following materials were employed in the grease preparation. Thesaponifiable material employed was a commercial 12-hydroxystearic acid,having a saponification number of 186, a neutralization number of 177and an iodine number of 3. The lubricating oil was a blend having aSaybolt Universal viscosity at 210 F. of about 84 seconds, obtained byblending 35 percent by volume of a paraffinic distillate oil, having aSaybolt Universal viscosity at F. in the range l75190 seconds, with asteam refined and deasphalted Manvel residuum having a Saybolt Universalviscosity at 210 F. in the range -163 seconds. The saponifying agentemployed was an aqueous lithium hydroxide solution comprising 9.3percent of lithium hydroxide.

Following is a detailed description of the procedure employed in thispreparation. A solution comprising 14 percent by weight of the12-hydroxystearic acid in lubricating oil preheated in the charge tankto 203 F. was charged to the reactor at a rate of 86.2 pounds per hourand the aqueous lithium hydroxide solution at room temperature wascharged to the reactor at a rate of 12.8 pounds per hour. The mixture inthe reaction zone was heated to 310 F. under a pressure of 70 pounds persquare inch at the reactor coil inlet and of 68 pounds per square inchat the reactor coil outlet. The recycle pump was operated at 18 gallonsper minute, resulting in a recycle ratio of 80:1. A product stream wastaken from the recycle stream and passed with pressure release throughthe back pressure valve to the dehydrator, where it was heated to 365 F.under a vacuum of 15 inches of mercury. The grease mixture in thedehydration zone was recycled at a rate of 18 gallons per minute withthe valve in the recycle line set to give a pressure drop of about 67pounds per square inch. Additional lubricating oil preheated in thestorage tank to 344 F. was introduced into the recycle stream at theinlet side of the recycle pump at a rate of 161.8 pounds per hour.

The volume of grease mixture in the dehydration zone was maintained atabout 0.84 cubic foot, which resulted in an average residence time of 10minutes for the grease mixture in the dehydration zone, during whichtime it was recycled through the recycle line an average of 28.6 times,i.e., an average of 28.6 turnovers of grease mixture during the averageresidence time.

A product stream was taken from the recycle stream at the discharge sideof the recycle pump and recycled through the cooler until it was cooledto 200 F.

A smooth grease of excellent texture and appearance was obtained asdescribed above in a total preparation time of 15.3 minutes. Thefollowing analyses and test results were obtained upon this grease.

Composition, percent:

The above data show that a very satisfactory grease was made with atotal average residence time in the continuous grease making unit ofonly 15 .3 minutes. This compares with an average time of about 11.4hours required for commercial preparation of a lithium12-hydroxystearate grease by a conventional low temperature process. Thegrease was furthermore obtained in optimum yield, as shown by the factthat a portion of the grease which was subjected to milling with onepass through a Premier colloid mill at 0.003 inch clearance had a workedpenetration of 284, or substantially the same as the unmilled product.

EXAMPLE II A calcium 12-hydroxystearate thickened grease was prepared bythe method of this invention as described below.

The apparatus employed was the same as that described in Example I.

The following materials were employed in the preparation. Thesaponifiable material was a commercial 12- hydroxystearic acid asdescribed in Example I. The mineral oil employed was a paraflinicdistillate oil having a Saybolt Universal viscosity at 100 F. of about347 seconds and a small amount, equal to about 1 percent of the finishedgrease of a Manvel residum having a Saybolt Universal viscosity at 210F. of 55 seconds. The saponifying agent was lime employed in the form ofa percent slurry in lubricating oil.

Following is a detailed description of the method employed in thepreparation. A 20.3 percent solution of the saponifiable material inlubricating oil preheated to 200 F. was charged to the reaction zone ata rate of 87.6 pounds per hour and the slurry of lime in lubricating oilat room temperature was charged at a rate of 23.8 pounds per hour. Thereaction mixture in the reaction zone was heated to 261 F. under apressure of 70 pounds per square inch (coil inlet) to 50 pounds persquare inch (coil outlet). Recycling on the reactor was carried out at18 gallons per minute, resulting in a recycle ratio of 66:1. The productstream, having a calculated soap content of 17.2 percent, was introducedinto the dehydrator where it was maintained at 282 F. and under a vacuumof 5.0 inches of mercury. The grease mixture was recycled from thebottom to the top of the dehydration zone at a rate of 18 gallons perminute by means of a recycle line containing a recycle pump and a valveoperated with a pressure drop of about 63 pounds per square inch.Additional lubricating oil preheated to 283 F. was introduced into therecycle stream at the inlet side of the recycle pump at a rate of 138pounds per hour. A volume of about 0.88 cubic foot was maintained in thedehydration Zone, which resulted in an average residence time of thegrease mixture of 10.7 minutes, during which time it was recirculatedthrough the recycle line for an average of 29.2 times. The productstream from the dehydration The materials employed were the following.The sapongallons per minute, resulting in 30 passes of the reactionmixture through the cooling zone. The grease mixture was cooled in thismanner to 195 F.

A smooth buttery grease was obtained in the above manner. The followinganalyses and test results were obtained upon this grease.

Composition, percent:

The above data show that a grease of satisfactory lubricating propertieswas obtained in good yield in the preparation, wherein the averageoverall time was only about 15.3 minutes. In addition, difiicultiesencountered in prior art processes in obtaining greases of this type insatisfactorily smooth form are overcome by carrying out the preparationin the manner described.

EXAMPLE III A sodium tallowate grease was prepared by the method of thisinvention as described below.

The apparatus employed was the same as that employed in the preparationdescribed in Example I except that a shear valve was provided in thefinishing section as shown in FIG. 1.

The materials employed were the following. The saponifiable materialemployed was a commercial high acid hard tallow. Typical tests upon thismaterial include a saponification number of 200, a free fatty acidcontent of 4.2 percent, an iodine number of 52 and a titer of 41.6 C.The lubricating oil employed was a deasphalted and dewaxed residuum froma paraffin base crude having a Saybolt Universal viscosity at 210 F. ofabout 189 seconds. The saponifying agent was sodium hydroxide in theform of a 49 percent aqueous solution.

Following is a detailed description of the method employed in thepreparation. Streams of saponifiable material and lubricating oilpreheated to 210 F. were charged to the saponification zone at rates of0.296 pound per minute and 0.557 pound per minute, respectively, whilethe alkali solution at room temperature was charged at 0.086 pound perminute. The reaction mixture was heated in the reactor to 333 F. under apressure of 155 pounds per square inch (coil inlet) to pounds per squareinch (coil outlet). Recycling on the reactor was carried out at a rateof 18 gallons per minute, resulting in a recycle ratio of 144:1. Theproduct stream, having a calculated soap content of 30.8 percent, wasintroduced into the dehydrator where it was maintained at 364 F. andunder a vacuum of 20 inches of mercury while it was recycled at a rateof 18 gallons per minute through the recycle line with the shear valveset to give a pressure drop of 70 pounds per square inch. No additionaloil was added to the grease mixture in the dehydrator in thispreparation.

The level of the grease mixture in the dehydrator was maintained atabout 15 inches, resulting in an average residence time of the greasemixture of 49.4 minutes, during which time the grease mixture wassubjected to an average of 144 passes through the recycle line.

The dehydrated product stream withdrawn from the dehydrator was cooledby the addition of lubricating oil at a lower temperature and recycledthrough the shear valve with a recycle rate of gallons per minute,resulting in a recycle ratio of 14:8:1 and a total time of the greasemixture in the finishing section of 0.44 minute. Circulation through thecooler was not employed in this preparation. The additional oil at 190F. was introduced into the stream of grease mixture at a rate of 4.150pounds per minute. The shear valve in the recycle line was set to give apressure drop of 140 pounds per square inch. The product stream waswithdrawn from the finishing section at 195 F.

A grease having the smooth slightly stn'ngy texture desired in a sodiumbase grease of this type and superior lubricating properties wasobtained as described above. The following analyses and tests wereobtained upon this product.

Composition, percent:

Sodium soap 5.3

Shell roll tests-Penetration point change +12 The above tests show thata sodium tallowate thickened grease was obtained in a good yield and ina greatly shortened manufacturing time by the method of our invention,the total time required by our method being about 1 hour, as comparedwith over 21 hours required for making a commercial batch of this greasein a conventional grease kettle. In addition, the grease prepared by ourprocess was superior in certain respects, particularly in shearstability, to the conventionally prepared greases, as shown by the factthat it underwent only 12 points penetration change in the Shell rolltests, as compared with 24-65 points penetration change of theconventionally prepared products.

Obviously, many modifications and variations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof, and therefore, only such limitation should be imposed asare indicated in the appended claims.

We claim:

1. A continuous process for manufacturing lubricating grease whichcomprises continuously introducing a reaction mixture consistingessentially of saponifiable material and metal base into a tubularreaction zone wherein the said mixture is maintained at a temperature of180 F. to above the melting point of the soap formed in the reaction andat a pressure of between 10- and 300 pounds per square inch gauge underturbulent conditions characterized by a Reynolds number of at least4,000 for a period sufiicient to obtain at least substantially completereaction, continuously withdrawing a product stream from the reactionzone, introducing into the product stream any lubricating oil requiredto give a grease mixture containing at least about 10 percent oflubricating oil, continuously introducing said grease mixture comprisinglubricating oil and soap into a dehydration zone wherein the greasemixture is maintained at an elevated temperature above about 225 F. butbelow the melting point of the soap and under a pressure substantiallylower than the pressure in the reaction zone, maintaining the saidgrease mixture in the dehydration zone for a period sufiicient toaccomplish at least substantially complete dehydration, adding anyadditional lubricating oil required to provide a grease mixturecomprising at least about 25 percent of lubricating oil, continuouslywithdrawing a product stream from the said dehydration zone, cooling thesaid withdrawn stream and mixing it with any additional lubricating oilrequired to provide a grease of the desired grade, said grease mixturein the said dehydration zone being circulated from the bottom to the topof the said dehydration zone through a recycle line containing a shearvalve operated with a pressure drop across the said valve of about10-200 pounds per square inch at a rate such that the volume of recycledgrease mixture during the average residence time of the grease mixturewithin the dehydration zone equals at least about 5 times the totalaverage volume of grease mixture within the said zone.

2. The process of claim 1 wherein the said reaction mixture is passedthrough the said tubular reaction zone at a rate within the range fromabout 0.6 to about 12.0 cubic feet per minute per square inch of reactorcross sectional areas.

3. The process of claim 1 wherein preheated oil is added to the saidgrease mixture within said dehydration zone.

4. The process of claim 1 wherein the said preheated oil is added to thesaid grease mixture in the said dehydration zone recycle line.

5. The process of claim 1 wherein the said product stream from the saiddehydration zone is cooled by the addition of lubricating oil.

6. The process of claim 5 wherein the said product stream from saiddehydration zone and any additional lubricating oil are subjected to ashearing operation.

7. The process of claim 1 wherein the said reaction mixture comprises aminor proportion of water.

8. The process of claim 1 wherein the said metal base is selected fromthe class consisting of oxides, hydroxides and carbonates of alkalimetals and alkaline earth metals.

9. A continuous process for maunfacturing lubricating greases whichcomprises continuously introducing a reaction mixture consistingessentially of saponifiable material, lubricating oil comprising atleast about 10 percent by weight of the said mixture, metal base, and aminor amount of water, into a reaction zone wherein the said mixture ismaintained at an elevated temperature in about the range 200-350 F.,under superatmospheric pressure of about 20-200 pounds per square inchand in a highly turbulent condition characterized by a Reynolds numberof at least 4,000 for a period sufiicient to obtain at leastsubstantially complete reaction between the said saponifiable materialand the said metal base, continuously Withdrawing a product stream ofthe grease mixture from the said reaction zone and introducing the saidwithdrawn stream into a dehydration zone wherein the grease mixture ismaintained at an elevated temperature in the range from about 250 F. tojust below the melting point of the soap contained in the said greasemixture and under a partial vacuum in the range from about 5 to 25inches of mercury, maintaining the said grease mixture in the saiddehydration zone for a period sufiicient to accomplish at leastsubstantial dehydration, adding any additional lubricating oil requiredto provide a grease mixture comprising at least about 40 percent oflubricating oil, continuously withdrawing a product stream from the saiddehydration zone, cooling the said withdrawn stream and mixing it withany additional lubricating oil required to provide a grease of thedesired grade, said grease mixture in the said dehydration zone beingcirculated from the bottom to the top of the said dehydration zonethrough a recycle line containing a shear valve operated with a pressuredrop of about 20-125 pounds per square inch across the said valve at arate such that the volume of recycled grease mixture during the averageresidence time of the grease mixture in the dehydration zone equals atleast about times the total average volume of grease mixture within thesaid zone.

10. The process of claim 9 wherein the said metal base is selected fromthe group consisting of oxides, hydroxides and carbonates of alkalimetals and alkaline earth metals.

11. The process of claim 1 wherein said reaction mixture comprises aminor portion of lubricating oil.

12. Apparatus for the continuous manufacture of a lubricating greasewhich comprises in combination, a tubular reaction zone, means forsupplying heat to said reaction zone, a dehydration zone of relativelylarge crosssectional area in comparison with the cross-sectional area ofsaid reaction zone, means for supplying heat to said dehydration zone,means for continuously introducing into said reaction zone at anelevated pressure saponifiable material and metal base reactants inrelative proportions to effect saponification of said reactants at anelevated pressure and temperature under turbulent flow conditionscharacterized by a Reynolds number of at least 4000, means forcontinuously discharging saponified reaction product from said reactionzone, means for continuously introducing lubricating oil into saiddischarged reaction product as required to provide a grease mixturecontaining at least about 10% by weight of lubricating oil, means forcontinuously introducing said grease mixture into said dehydration zonemaintained at a substantially lower pressure than said reaction zone,means for continuously withdrawing a portion of the resulting dehydratedgrease mixture from a lower part of said dehydration zone and passingsaid withdrawn portion through a restricted orifice effecting shearingthereof and returning said sheared portion to an upper part of saiddehydration zone, and means for continuously discharging the resultingsheared grease mixture from said dehydration zone.

13. Apparatus as claimed in claim 12 wherein said reaction zone isprovided with means for continuous withdrawal of a portion of saidsaponified reaction product from said reaction zone and return of saidwithdrawn portion to said reaction zone.

14. Apparatus as claimed in claim 13 wherein said means for withdrawinga portion of said saponified reaction product from said reaction zone isprovided with means for introducing lubricating oil into said withdrawnportion.

15. Apparatus as claimed in claim 12 wherein said dehydration zone isprovided with means for introducing additional lubricating oil directlyinto said dehydration zone.

16. Apparatus as claimed in claim 12 wherein said means for continuouswithdrawal of a portion of the dehydrated grease mixture from saiddehydration zone is provided with means for introducing lubricating oilinto the said withdrawn portion.

17. Apparatus as claimed in claim 12 wherein said means for continuouslydischarging the resulting dehydrated grease mixture from saiddehydration zone is provided with means for introducing lubricating oilinto the discharged mixture.

18. Apparatus as claimed in claim 12 wherein said means for dischargingsaid dehydrated grease mixture from said dehydration zone is providedwith a restricted orifice elfecting a pressure drop of the order of 20to 200 p.s.i. to effect shearing of said mixture.

19. Apparatus as claimed in claim 12 including means for cooling saiddischarged dehydrated grease mixture.

20. Apparatus as claimed in claim 19 wherein said cooling meanscomprises means for introducing lubricating oil into said shearedmixture.

References Cited UNITED STATES PATENTS 2,298,317 10/ 1942 Smith 252392,374,913 5/ 1945 Beerbower et al. 25239 2,383,906 8/1945 Zimmer et al.25239 2,886,525 5/1959 Dilworth et .al. 25239 3,068,175 12/1962 Roach etal. 25241 3,242,083 3/ 1966 Crookshank et al. 25241 2,298,317 10/1942Smith 25239 2,332,202 10/ 1943 Calkins 25242.1 2,374,913 5/1945Beerbower et al. 25239 2,383,906 8/ 1945 Zimmer et al. 25239 2,450,2209/1948 Ashburn et al. 25241 2,652,366 9/1953 Jones et al 25239 X2,830,022 4/ 1958 Nelson et al. 25241 2,870,090 1/1959 Pitman et al.25239 X 2,886,525 5/ 1959 Dilworth et al. 25239 3,015,624 1/1962 Henckeet al. 25241 3,068,174 12/ 1962 Pelton et .al. 25239 3,068,175 12/1962Roach et al. 25239 3,079,341 2/1963 Coons Jr. et al. 25241 3,117,0871/1964 McCormick et al. 25241 3,242,083 3/ 1966 Crookshank et al. 25241DANIEL E. WYMAN, Primary Examiner I. VAUGHN, Assistant Examiner US. Cl.X.R. 25235, 41

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3475335Dated October 1969 John H. Greene, William R. Hencke, lnventofls)Clarence L. Dowden, Jr. and Herbert J. Pitman It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

COLUMN 1, before line 30, insert as a separate paragraph --Thisapplication is a continuation of application Serial No. 333,164 filedDec. 24, 1963 and now abandoned. COLUMN 9, line 53, "residum" shouldread --residuum--. COLUMN 10, line 9, delete "The materials employedwere the following. The sapon-" and substitute --zone was recycledthrough the cooler at a rate of 18--. COLUMN 12, line 23, "areas" shouldread --area--.

3mm SEALED Auszsm (SEAL) An mm; x. edawm, JR- Edwar lLFIcm emission m

